Wiggling Through the World

Many reptiles make their way without the use of limbs. Slithering may look like a relatively simple process, but Goldman and Hu have discovered that even when body movements look similar, the physical forces propelling the animals forward are quite different depending on the substrate the animal is moving on or through. The authors describe how their experimental laboratory work (which uses x-ray cameras, mirrors, gels that transmit light only when pushed and snake full-body socks) and theoretical models have elucidated the mechanisms of two distinct kinds of movement: the slithering of snakes above ground and the “swimming” of a lizard called a sandfish within flowing substrates such as sand.